8301893: IME window position is off on secondary screen

Reviewed-by: kcr, angorya

Author: Martin Fox

modules/javafx.graphics/src/main/native-glass/mac/GlassView3D.m

@@ -810,8 +810,10 @@ - (NSRect) firstRectForCharacterRange:(NSRange)theRange actualRange:(NSRangePoin
     IMLOG("firstRectForCharacterRange called %lu %lu",
           (unsigned long)theRange.location, (unsigned long)theRange.length);
     NSRect result = [self->_delegate getInputMethodCandidatePosRequest:0];
-    NSRect screenFrame = [[NSScreen mainScreen] frame];
-    result.origin.y = screenFrame.size.height - result.origin.y;
+    if (NSScreen.screens.count) {
+        NSRect screenFrame = NSScreen.screens[0].frame;
+        result.origin.y = screenFrame.size.height - result.origin.y;
+    }
     return result;
 }